v3.26.3
Cover
Sep. 23, 2026
Document Information [Line Items]  
Document Type S-1
Amendment Flag false
Entity Information [Line Items]  
Entity Registrant Name Frazier Life Sciences Acquisition Corp. II
Entity Central Index Key 0002153598
Entity Primary SIC Number 6770
Entity Tax Identification Number 98-1964369
Entity Incorporation, State or Country Code E9
Entity Filer Category Non-accelerated Filer
Entity Small Business true
Entity Emerging Growth Company true
Entity Ex Transition Period false
Entity Contact Personnel [Line Items]  
Entity Address, Address Line One 1001 Page Mill Road,
Entity Address, Address Line Two Building 4, Suite 200B
Entity Address, City or Town Palo Alto
Entity Address, State or Province CA
Entity Address, Postal Zip Code 93404
Entity Phone Fax Numbers [Line Items]  
City Area Code 650
Local Phone Number 325-5156
Business Contact [Member]  
Entity Contact Personnel [Line Items]  
Contact Personnel Name Albert Cha
Entity Address, Address Line One 1001 Page Mill Road,
Entity Address, Address Line Two Building 4, Suite 200B
Entity Address, City or Town Palo Alto
Entity Address, State or Province CA
Entity Address, Postal Zip Code 93404
Entity Phone Fax Numbers [Line Items]  
City Area Code 650
Local Phone Number 325-5156